Systems and methods for immersion-cooled datacenters

ABSTRACT

A thermal management system includes a server computer and a shell defining an immersion chamber. The shell contacts the server computer along a bottom side and lateral walls of the chamber, and the immersion chamber has an opening on a top side. The shell is connected to the server computer and a portion of the server computer defines at least a portion of the immersion chamber.

BACKGROUND Background and Relevant Art

Computing devices can generate a large amount of heat during use. Thecomputing components can be susceptible to damage from the heat andcommonly require cooling systems to maintain the component temperaturesin a safe range during heavy processing or usage loads. Liquid coolingcan effectively cool components as liquid working fluids have morethermal mass than air or gas cooling. The liquid working fluid can bemaintained at a lower temperature by allowing vaporized fluid to riseout of the liquid. The vapor in the cooling liquid can adversely affectthe cooling performance of the working fluid. The vapor can be condensedand returned to the immersion tank.

BRIEF SUMMARY

In some embodiments, a thermal management system includes a servercomputer and a shell defining an immersion chamber. The shell contactsthe server computer along a bottom side and lateral walls of thechamber, and the immersion chamber has an opening on a top side. Theshell is connected to the server computer and a portion of the servercomputer defines at least a portion of the immersion chamber.

In some embodiments, an immersion cooling system includes a collectiontank with a collection area, a substrate having at least oneheat-generating electronic component thereon, and a shell defining animmersion chamber. The shell contacts the server computer along a bottomside and lateral walls of the chamber, and the immersion chamber has anopening on a top side. The shell is connected to the server computer anda portion of the server computer defines at least a portion of theimmersion chamber. The substrate and heat-generating componentpositioned in the collection tank and above the collection area.

In some embodiments, a method of thermal management of electroniccomponents includes introducing a first amount of liquid working fluidto a liquid immersion bath in contact with a heat-generating componentof a computing device, boiling at least a vaporized portion of theliquid working fluid with the heat-generating component, and removing asecond amount of liquid working fluid less than the first amount.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

Additional features and advantages will be set forth in the descriptionwhich follows, and in part will be obvious from the description, or maybe learned by the practice of the teachings herein. Features andadvantages of the disclosure may be realized and obtained by means ofthe instruments and combinations particularly pointed out in theappended claims. Features of the present disclosure will become morefully apparent from the following description and appended claims or maybe learned by the practice of the disclosure as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otherfeatures of the disclosure can be obtained, a more particulardescription will be rendered by reference to specific embodimentsthereof which are illustrated in the appended drawings. For betterunderstanding, the like elements have been designated by like referencenumbers throughout the various accompanying figures. While some of thedrawings may be schematic or exaggerated representations of concepts, atleast some of the drawings may be drawn to scale. Understanding that thedrawings depict some example embodiments, the embodiments will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

FIG. 1 is a side schematic representation of an immersion coolingsystem, according to at least one embodiment of the present disclosure;

FIG. 2 is a side schematic representation of an immersion cooling systemwith an external condenser, according to at least one embodiment of thepresent disclosure;

FIG. 3-1 is a front schematic representation of an immersion coolingsystem, according to at least one embodiment of the present disclosure;

FIG. 3-2 is a side view of the immersion cooling system of FIG. 3-1 ;

FIG. 4 is a front schematic representation of another immersion coolingsystem, according to at least one embodiment of the present disclosure;

FIG. 5 is an exploded perspective view of a server computer and shellassembly, according to at least one embodiment of the presentdisclosure;

FIG. 6-1 is a perspective view of an immersion cooling system with aseries of server computer and shell assemblies, according to at leastone embodiment of the present disclosure;

FIG. 6-2 is a front partial cross-sectional view of the immersioncooling system of FIG. 6-1 ;

FIG. 7 is perspective view of a collection tank, according to at leastone embodiment of the present disclosure;

FIG. 8 is a flowchart illustrating a method of thermal management,according to at least one embodiment of the present disclosure;

FIG. 9 is a perspective view of a horizontally oriented server computerand shell assembly, according to at least one embodiment of the presentdisclosure;

FIG. 10 is a side view of an immersion cooling system with angled servercomputer and shell assemblies, according to at least one embodiment ofthe present disclosure; and

FIG. 11 is a front view of a server computer with a plurality ofimmersion chambers thereon with liquid working fluid cascadingtherebetween.

DETAILED DESCRIPTION

The present disclosure relates generally to systems and methods forthermal management of electronic devices or other heat-generatingcomponents. Immersion chambers surround the heat-generating componentsin a liquid working fluid, which conducts heat from the heat-generatingcomponents to cool the heat-generating components. As the working fluidabsorbs heat from the heat-generating components, the temperature of theworking fluid increases. In some embodiments, the working fluidvaporizes, introducing vapor into the liquid of the working fluid.

In large-scale computing centers, such as cloud-computing centers, dataprocessing centers, data storage centers, or other computing facilities,immersion cooling systems provide an efficient method of thermalmanagement for many computing components under a variety of operatingloads. In some embodiments, an immersion cooling system includes aworking fluid in an immersion chamber and a condenser to extract heatfrom the vapor of the working fluid. The condenser then condenses thevapor phase of the working fluid into a liquid phase and returns theliquid working fluid to the immersion chamber. In some embodiments, theliquid working fluid absorbs heat from the heat-generating components,and one or more fluid conduits direct the hot liquid working fluidoutside of the immersion chamber to a radiator or region of lowertemperature to cool the liquid working fluid.

Whether the immersion cooling system is a two-phase cooling system(wherein the working fluid vaporizes and condenses in a cycle) or aone-phase cooling system (wherein the working fluid remains in a singlephase in a cycle), the heat transported from the heat-generatingcomponents outside of the immersion chamber is further exchanged with anambient fluid to exhaust the heat from the system.

A conventional immersion cooling system 100, shown in FIG. 1 , includesan immersion tank 102 containing an immersion chamber 104 and acondenser 106 in the immersion chamber 104. The immersion chamber 104contains a working fluid that has a liquid working fluid 108 and a vaporworking fluid 110 portion. The liquid working fluid 108 creates animmersion bath 112 in which a plurality of heat-generating components114 are positioned to heat the liquid working fluid 108 on supports 116.

Referring now to FIG. 2 , an immersion cooling system 200 according tothe present disclosure includes an immersion tank 202 defining animmersion chamber 204 with a working fluid positioned therein. Theworking fluid transitions between a liquid working fluid 208 phase and avapor working fluid 210 phase to remove heat from hot or heat-generatingcomponents 214 in the immersion chamber 204. The liquid working fluid208 more efficiency receives heat from the heat-generating components214 and, upon transition to the vapor working fluid 210, the vaporworking fluid 210 can be removed from the immersion tank 202, cooled andcondensed by the condenser 206 to extract the heat from the workingfluid, and the liquid working fluid 208 can be returned to the liquidimmersion bath 212.

In some embodiments, the immersion bath 212 of the liquid working fluid208 has a plurality of heat-generating components 214 positioned in theliquid working fluid 208. The liquid working fluid 208 surrounds atleast a portion of the heat-generating components 214 and other objectsor parts attached to the heat-generating components 214. In someembodiments, the heat-generating components 214 are positioned in theliquid working fluid 208 on one or more supports 216. The support 216may support one or more heat-generating components 214 in the liquidworking fluid 208 and allow the working fluid to move around theheat-generating components 214. In some embodiments, the support 216 isthermally conductive to conduct heat from the heat-generating components214. The support(s) 216 may increase the effective surface area fromwhich the liquid working fluid 208 may remove heat through convectivecooling.

In some embodiments, the heat-generating components 214 includeelectronic or computing components or power supplies. In someembodiments, the heat-generating components 214 include computerdevices, such as individual personal computer or server blade computers.In some embodiments, one or more of the heat-generating components 214includes a heat sink or other device attached to the heat-generatingcomponent 214 to conduct away thermal energy and effectively increasethe surface area of the heat-generating component 214. In someembodiments, the heat-generating components 214 include an electricmotor.

As described, conversion of the liquid working fluid 208 to a vaporphase requires the input of thermal energy to overcome the latent heatof vaporization and may be an effective mechanism to increase thethermal capacity of the working fluid and remove heat from theheat-generating components. Because the vapor working fluid 210 rises inthe liquid working fluid 208, the vapor working fluid 210 can beextracted from the immersion chamber 204 in an upper vapor region of thechamber. A condenser 206 cools part of the vapor working fluid 210 backinto a liquid working fluid 208, removing thermal energy from the systemand reintroducing the working fluid into the immersion bath 212 of theliquid working fluid 208. The condenser 206 radiates or otherwise dumpsthe thermal energy from the working fluid into the ambient environmentor into a conduit to carry the thermal energy away from the coolingsystem.

In conventional immersion cooling systems, a liquid-cooled condenser isintegrated into the immersion tank and/or the chamber to efficiencyremove the thermal energy from the working fluid. In some embodimentsaccording to the present disclosure, an immersion cooling system 200 forthermal management of computing devices allows at least one immersiontank 202 and/or chamber 204 to be connected to and in fluidcommunication with an external condenser 206. In some embodiments, animmersion cooling system includes a vapor return line 218 that connectsthe immersion tank 202 to the condenser 206 and allows vapor workingfluid 210 to enter the condenser 206 from the immersion tank 202 and/orchamber 204 and a liquid return line 220 that connects the immersiontank 202 to the condenser 206 and allows liquid working fluid 208 toreturn to the immersion tank 202 and/or chamber 204.

The vapor return line 218 may be colder than the boiling temperature ofthe working fluid. In some embodiments, a portion of the vapor workingfluid condenses in the vapor return line 218. The vapor return line 218can, in some embodiments, be oriented at an angle such that the vaporreturn line 218 is non-perpendicular to the direction of gravity. Thecondensed working fluid can then drain either back to the immersion tank202 or forward to the condenser 206 depending on the direction of thevapor return line 218 slope. In some embodiments, the vapor return line218 includes a liquid collection line or valve, like a bleeder valve,that allows the collection and/or return of the condensed working fluidto the immersion tank 202 or condenser 206.

In some examples, an immersion cooling system 200 includes an air-cooledcondenser 206. An air-cooled condenser 206 may require fans or pumps toforce ambient air over one or more heat pipes or fins to conduct heatfrom the condenser to the air.

FIG. 3-1 is a schematic representation of an immersion cooling system300 with localized immersion chambers 304 on a server computer 324 tocapture and pool liquid working fluid 308 adjacent the greatestheat-generating components 314. Working fluid is recycled through thethermal management system, and, in some embodiments, the working fluidis a dielectric fluid or other fluid that is expensive. A thermalmanagement system that uses less working fluid and/or uses the workingfluid more efficiently allows for cost savings in the working fluid. Insome embodiments, the working fluid is relatively dense and containinglarge volumes of the working fluid requires a strong container. Buildingand maintaining containers for large volumes and/or masses of workingfluid can increase construction costs and container weight, which limitstransport and maintenance of the containers.

In some embodiments according to the present disclosure, a shell 326 isattached to a server computer 324 or other electronic device to captureand pool the liquid working fluid 308 adjacent to at least oneheat-generating component 314 of the server computer 324 in an immersionchamber 304. In some embodiments, the shell 326 is a stamped metal orpolymer sheet. In some embodiments, the shell 326 is an injection moldedsheet. The shell 326 may have planar or curved surfaces to define aportion of the immersion chamber 304. In some embodiments, the shell 326defines a portion of a rectangular prism or box-shaped immersion chamber304 around the heat-generating electronic components 314. In someembodiments, as will be described in relation to FIG. 5 , at least aportion of the shell 326 is contoured to follow the shape of theheat-generating electronic components 314.

In some embodiments, the shell 326 contacts the server computer 324 or asubstrate 328 of the server computer 324 along a bottom side 330 andlateral walls 332 of the immersion chamber 304 to collect the liquidworking fluid 308. A top side 334 of the shell 326 has an opening 336therein to the immersion chamber 304. The top side 334 of the shell 326is the side, edge, or portion of the shell 326 that is oriented upwardrelative to a direction of gravity such that vapor working fluid 310bubbles rise through the immersion chamber 304 toward the top side 334.In some embodiments, the opening 336 in the top side 334 allows thevapor working fluid 310 to exit the immersion chamber 304. In someembodiments, the top side 334 is a planar surface of the shell 326. Insome embodiments, the top side 334 follows a top edge of the shell 326.

The opening 336 allows incoming liquid working fluid 338 to beintroduced to the immersion chamber 304 and fill the immersion chamber304 with liquid working fluid 308. In some embodiments, the incomingliquid working fluid 338 continuously fills the immersion chamber 304 toprevent a liquid level of the liquid working fluid 308 from fallingbelow the heat-generating components 314. In some embodiments, theincoming liquid working fluid 338 continuously fills the immersionchamber 304 to prevent a liquid level of the liquid working fluid 308from falling below the lowest part of the opening 336. For example, theincoming liquid working fluid 338 may continuously fill the immersionchamber 304 such that liquid working fluid spills out of the immersionchamber by overflowing the opening 326, leaking from a contactinterface, exiting through one or more apertures or perforations 340,through a drain, or combinations thereof.

In some embodiments, a portion of the liquid working fluid 308continuously overflows from the opening 336 as incoming liquid workingfluid 338 flows into the immersion chamber 304 through the opening 336.A flow rate of the incoming liquid working fluid is at least greaterthan vaporization rate of the liquid working fluid in the immersionbath. In other words, more liquid working fluid mass is introduced intothe immersion bath that is boiled by the heat-generating components,such that at least a portion of the liquid working fluid is displacedfrom the immersion bath by the incoming liquid working fluid.

In some embodiments, at least part of the liquid working fluid 308 flowsout of the immersion bath 304 through one or more apertures, gaps, orperforations 340 in the lateral walls 332 and/or bottom side 330 of theimmersion chamber 304. For example, a contact interface between theshell 326 and the server computer 324 may be not liquid tight, andallows at least a portion of the liquid working fluid 308 in theimmersion chamber 304 to flow out of the immersion chamber 304 at thecontact interface between the shell 326 and the substrate 328 of theserver computer 324. In some embodiments, the shell 326 includes one ormore perforations 340 through the shell 326, itself, that allows liquidworking fluid 308 to leak through the perforations 340. In someembodiments, the shell 326 includes a drain that may be selectivelyopened or closed to adjust the volume of liquid cooling fluidoverflowing from the opening of the immersion chamber.

As described herein, the incoming working fluid 338 may be colder thanthe liquid working fluid 308 in the immersion chamber 304, and thecolder incoming working fluid 338 may cool the heat-generatingcomponents 314 more efficiently. Allowing at least a portion of theliquid working fluid to exit the immersion chamber through gaps,perforations, or drains in the shell or immersion chamber may allowgreater mixing of the liquid working fluid in the immersion chamber,and, therefore, a lower average temperature of the liquid working fluidin the immersion chamber.

In some embodiments, a flow rate of the incoming liquid working fluid338 is greater than vaporization rate of the liquid working fluid in theimmersion bath and a flow rate of all liquid flow out of the immersionchamber other than overflow through the opening, such that the liquidlevel of the immersion chamber remains above the heat-generatingcomponents and/or at the lowest point of the opening.

The server computer 324 may have a plurality of heat-generatingelectronic components 314 affixed to a substrate 328, such as amotherboard. Some electronic components may consume more power and/orgenerate more heat than other components. The greatest heat-generatingcomponents 314 of the server computer 324 may be immersed in liquidworking fluid 308, while lesser heat-generating components 342 may becooled through ambient gas cooling (e.g., a fan blowing on the lesserheat-generating components) or through overflow liquid working fluid 308flowing from the immersion chamber 304 defined by the shell 326.

The liquid working fluid introduced into the immersion chamber has atemperature less than the boiling temperature of the working fluid. Whena portion of the working fluid overflows from the immersion chamber, theoverflow liquid working fluid will still have an average temperaturebelow the boiling temperature. The overflow liquid working fluid maythen cool the lesser heat-generating components by absorbing heat fromthe lesser heat-generating components before boiling.

In some embodiments, the collection tank 302 includes condensers 306positioned in the vapor space of the collection tank 302 above a liquidcollection area 344. At least a portion of the condenser 306 may bepositioned in the bottom half of the collection tank 302. In someembodiments, all of the coils 346 or cold plates of the condenser 306may be positioned in the bottom half of the collection tank 302. In someembodiments, at least a portion of the condenser 306 may be below theopening in the immersion chamber defined by the shell. In someembodiments, all of the coils or cold plates of the condenser may bepositioned in the bottom half of the collection tank below the openingin the immersion chamber defined by the shell.

Vapor working fluid 310 condensed by the condensers 306 falls to acollection area 344 in the bottom of the collection tank 302. Thecollection area 344 also collects the liquid working fluid 308 that isdisplaced from the immersion chamber 304. The collected liquid workingfluid may be returned to the immersion chamber through a liquid returnline 320. In some embodiments, the liquid working fluid may be furthercooled while passing through the liquid return line 320 beforere-entering the immersion chamber.

By lowering the condensers 306 in the collection tank 302, lessheadspace is required above the server computers, which reduces the sizeof the collection tanks needed to house the components. For example, thecondensers can be move away from the lid, allowing the lid to be lighterand easier to remove to access the interior volume of the thermalmanagement system. In at least one embodiment, the headspace above theheat-generating component 314 and/or the server computer 324 is lessthan the width of the collection tank 302. Conventional immersioncooling systems require a headspace above the components as much as 1.5times the width of the tank.

In some embodiments, lowering the condensers in the collection tankallows the condensers to more efficiently condense the vapor workingfluid. The vapor working fluid may be denser that non-condensable gases,such as nitrogen, that may enter the collection tank. Thenon-condensable gases can collect above the server computer(s) and theimmersion tank(s) while the vapor working fluid settles lower in thecollection tank. The condensers may be positioned in the area of thecollection tank with a higher concentration of the vapor working fluid.

The presence of non-condensable gases can adversely affect theperformance of the thermal management system, as the condensation of thevapor working fluid to a liquid working fluid lowers the pressure in thecollection tank, helping to draw the incoming liquid working fluid intothe collection tank. For example, the liquid working fluid may be over100 times denser (i.e., take up less than 1/100^(th) of the volume) thanvapor working fluid. In some embodiments, the non-condensable fluidsseparating into the headspace above the top of the immersion chambersand/or the server computers can allow the non-condensable gases to bevented, pumped, or otherwise purged from the collection tank moreefficiently through a non-condensable gas vent 322.

In some embodiments, removing at least a portion of the server computersor other electronic devices from the immersion bath or collection bathcan maintain a cleaner, and, therefore, more efficient, working fluid.For example, the elastomers found in electronic connectors, wires,cables, or other components can leach into the liquid working fluid morereadily than into the vapor working fluid. The leached elastomers canadversely affect the thermal absorption efficiency of the working fluid,adversely affect the viscosity of the working fluid, adversely affectthe boiling temperature of the working fluid, or cause the working fluidto leave a deposit on the heat-generating components, which canadversely affect the thermal transfer (e.g., cooling) from theheat-generating components.

In some embodiments, data connectivity may be improved by positioningthe connectors of the server computer in a gaseous environment relativeto a liquid environment. For example, optical connections, such as fiberoptics, may perform better and/or more predictably in a gaseousenvironment relative to a liquid environment due to differences in theindex of refraction between the optical fibers and the liquidenvironment.

In a conventional immersion tank, the liquid pressure increases as depthof the immersion bath increases. In conventional tanks and fluids, adepth of 1 meter results in a 2.3 pounds per square inch (PSI) increase.The increased pressure results in an increase in the boiling point forthe working fluid and a resulting temperature increase of the componentsadjacent the working fluid at the bottom of the immersion bath. Whenseparate immersion chambers are placed around heat-generatingcomponents, and/or the boards are oriented horizontally, the columnarpressure of the fluid around the component is reduced and produces loweroperating temperatures for the component. In at least one example, aworking fluid exhibits a 4° C. decrease in temperature relative to acomponent at a depth of 1 meter in a conventional immersion tank.

The incoming liquid working fluid is delivered by, in some embodiments,a manifold that directs the incoming liquid working fluid into theimmersion chamber. In some embodiments, the incoming liquid workingfluid is introduced through the opening in the top surface of theimmersion chamber. In some embodiments, the incoming liquid workingfluid is introduced through a port in shell, such as in the lateral wallof the immersion chamber. The incoming liquid working fluid may displacethe liquid working fluid in the immersion chamber, at least partially,out the opening in the top.

FIG. 3-2 is a side view of the thermal management system of FIG. 3-1 ,illustrating a plurality of server computers 324 and shells 326 inseries. The manifold 346 may provide incoming liquid working fluid 338to each of the shells 326 and immersion chambers 304, individually. Theindividual immersion chamber 304 for each server computer 324 is a moreefficient allocation of liquid working fluid while also providingmodularity in the immersion cooling system for maintenance and repairs.

FIG. 4 is a schematic representation of another embodiment of animmersion cooling system 400. In some embodiments, the manifold 446 canprovide a plurality of streams 448 of incoming liquid working fluid 438that are directed at the immersion chamber 404 to fill the immersionchamber 404. The plurality of streams 448 may allow for additionalcooling on other lesser heat-generating components 442. The plurality ofstreams 448 may provide greater turbulence and mixing of the incomingliquid working fluid 438 with the liquid working fluid 408 in theimmersion chamber to limit and/or prevent temperature gradients in theimmersion chamber.

In some embodiments, the condenser 406 includes a plurality of coolingpipes 450 or cooling rods. The condenser 406 most efficiently cools andcondenses vapor immediately adjacent to a surface of the pipes 450 orrods. In some embodiments, deflectors 452 are positioned below at leastone of the pipes 450 or rods to catch condensate 454. The deflector 452limits and/or prevents the condensate 454 from falling onto the pipe 450or rod below, which would coat, and adversely affect the condensationefficiency of, the subsequent pipe 450 or rod.

In some embodiments, at least a portion of the heat-generatingcomponents in the immersion cooling system protrude above the immersionbath of liquid working fluid. Cooling of the heat-generating componentsmay be assisted by the spraying of liquid working fluid toward and/orabove the heat-generating components. In some embodiments, a fluidconduit carries liquid working fluid from the collection bath or otherreservoir of liquid working fluid to at least one nozzle, such as on themanifold 446 described herein. The liquid working fluid is ejected fromthe nozzle(s) in droplets toward an immersion chamber and/or othercomponents of the server computers.

The nozzles may be configured and/or sized to produce droplets of adesired diameter. The nozzles may be adjustable to vary the size of thedroplets depending upon desired flowrate through the nozzles and thedesired droplet size. In some embodiments, the nozzles create aplurality of droplets with an average droplet diameter of less than 1millimeter. In some embodiments, the nozzles create a plurality ofdroplets with an average droplet diameter of less than 0.5 millimeters.In some embodiments, the nozzles create a plurality of droplets with anaverage droplet diameter of less than 0.25 millimeters. In someembodiments, the nozzles create a plurality of droplets with an averagedroplet diameter of less than 0.1 millimeters. In some embodiments, thenozzles sprays the subcooled working fluid onto another component, suchas a fan, which further disrupts the surface tension and creates thedroplets and/or more droplets to introduce the liquid working fluid tothe server computers.

To further improve efficiency of working fluid allocation, in someembodiments, the shell is complementarily shaped to a topography of atleast one heat-generating component, such as illustrated in FIG. 5 . Forexample, the heat-generating components 514 may protrude from thesubstrate 528 by different degrees, such as a memory module protrudingfarther than a processor. In some embodiments, the shell 526 iscomplementarily shaped to the heat-generating components 514 to maintaina substantially constant distance from the heat-generating components514 and, therefore, a substantially constant amount of liquid workingfluid around the heat-generating components 514. In some embodiments,the shell 526 includes a vapor direction feature on an inner surface 556thereof to collect and direct the vapor bubbles around or through theheat-generating components 514 to reduce dryout as the vapor bubblesrise through the immersion chamber.

The shell 526 may be supported against or adjacent to the servercomputer and/or substrate 528 by a frame 557. In some embodiments, theframe 557 is a chassis of the server computer. In some embodiments, theframe 557 is supported by or supports the chassis of the server. In someembodiments, the frame 557 defines at least part of the immersionchamber, such as a lateral wall of the immersion chamber.

FIG. 6-1 and FIG. 6-2 are a perspective view and an end view,respectively, of an immersion cooling system 600 with a series of servercomputers 624 in a collection tank 602. Collecting liquid working fluidadjacent to each server computer 624 in a rack or collection tank 602simplifies maintenance and/or modifications to the server array. In aconventional immersion cooling system, the entire immersion tank may bedrained to access a component. In a conventional immersion coolingsystem, removing one server computer or other component removes volumefrom the immersion tank, lower the liquid level of the immersion bath,which may expose other components to a reduction in cooling capacity. Animmersion cooling system 600 according to the present disclosure allowseach server computer 624 to have discrete immersion chambers for eachserver computer, allowing the cooling of each server computer to beindependent of the presence or removal of other components or computers.

A reduction in liquid working fluid mass, and liquid working fluid levelin the collection tank, reduces the hydrostatic pressure against thewalls of the immersion chamber. For example, replacing the liquidworking fluid in the tank with vapor working fluid may reduce thepressure on the collection tank 602 by over 100 times, allowing forlighter, smaller, and cheaper tanks to be used. In some embodiments, theworking fluid is 1.8 times to 2.0 times denser than water. Less workingfluid mass means less hydrostatic pressure and less likelihood of leaksor other failures of the collection tank 602.

Referring now to FIG. 6-2 , in some embodiments, the condenser 606 ispositioned on a bottom or a side of the collection tank 602. Because theliquid level of the collection area 644 is lower than the servercomputers 624 and the immersion chambers 604, the server computers 624can be accessed and/or removed from the collection tank 602 through atop of the collection tank 602 without moving or turning off thecondenser 606. In some embodiments, the liquid working fluid cancontinue cycling through the liquid return line and through the manifoldeven while one or more server computer and shell assemblies is removedor replaced, reducing downtime and preventing the need for virtualmachine migration.

While vertical access to the server computer and/or thermal managementsystem is possible from the top with some embodiments of the presentdisclosure, some embodiments of collection tanks allow access to thecollection tank, server computers, connectors, other components, orcombinations thereof through a front or side surface of the collectiontank, such as illustrated in FIG. 7 . For example, one or more movableor removable access panels 758 in a side wall 760 of the collection tank702 may have a bottom edge 762 that is higher that a liquid level of thecollection area 744 at the bottom of the collection tank 702. In someembodiments, the bottom edge 762 of the access panel 758 may be higherthan the liquid level to retain the relatively dense vapor working fluidin the collection tank 702.

Various embodiments and arrangements of components may be used toperform thermal management using a continuous flooding of liquid workingfluid. FIG. 8 illustrates a method of thermal management. In someembodiments, a method 864 of thermal management according to the presentdisclosure includes introducing a first amount of liquid working fluidto a liquid immersion bath in contact with a heat-generating componentat 866 and boiling at least a vaporized portion of the liquid workingfluid with the heat-generating component at 868. The liquid workingfluid absorbs heat from the heat-generating components and increases intemperature until reaching the boiling temperature. The liquid workingfluid absorbs heat to exceed the latent heat needed to transition statesto a gas.

While a vaporized portion of the working fluid transitions to a vaporand rises out of the liquid immersion bath from around theheat-generating components, another portion of the liquid working fluidin the immersion bath is removed from the immersion bath. In someembodiments, the method includes removing from the liquid immersion batha second amount of liquid working fluid less than the first amount thatis introduced into the liquid immersion bath at 870. By removing thesecond amount of liquid working fluid from the immersion bath whileintroducing the first amount, the immersion bath cycles liquid workingfluid. In some embodiments, the incoming liquid working fluid is colderthan the outgoing liquid working fluid, lowering the temperature of theimmersion bath.

In some embodiments, the mass of the first amount of liquid workingfluid is equal to the mass of the vaporized portion and the secondamount of liquid working fluid. In some embodiments, the second amountis removed from the liquid immersion bath by at least one of overflowfrom an opening at the top of the immersion chamber, flow out of one ormore contact interfaces between a shell and the computing device, flowout of one or more apertures or perforations in the shell or computingdevice, or through a drain that selectively opened or adjusted tocontrol flow therethrough.

The method may further include directing the second amount of the liquidworking fluid toward or onto other heat-generating components. In someembodiments, a shell and/or computing device that define an immersionchamber includes fluid direction features to control the flow oroverflow of the liquid working fluid upon exiting the immersion chamber.

FIG. 9 is a perspective view of an embodiment of a horizontal servercomputer 924 with liquid working fluid 908 overflowing from theimmersion chamber 904 and fluid direction features 972 to control flowof the liquid working fluid 908. While embodiments of verticallyoriented server computers and shells have been described herein, in someembodiments, the substrate 928 of the server computer 924 and/or theshell 926 are oriented substantially horizontally. For example, thehorizontal shell 926 may have a top side 934 (i.e., relative to adirection of gravity when positioned in a collection tank (such ascollection tank 602 of FIGS. 6-1 and 6-2 ) with an opening 936 that islarger in area that a vertically oriented shell and server computer. Thehorizontal server computer and heat-generating component, in combinationwith a larger opening, allows the vapor to exit the immersion chambermore efficiently. The horizontal server computer and heat-generatingcomponent, in combination with a larger opening, may reduce dryout andincrease cooling efficiency.

In some embodiments, the shell 926 includes at least one fluid directionfeature 972, such as a channel, groove, notch, opening, fin, wall, slot,tunnel, or other structure integrated into or located on a surface ofthe shell 926. The fluid direction feature 972 influences the directionof the liquid working fluid 908 as the liquid working fluid 908 exitsthe immersion chamber 904. In some embodiments, a surface of the servercomputer 924 and/or substrate 928 of the server computer includes atleast one fluid direction feature to further direct the liquid workingfluid toward a heat-generating component 942 located outside of theimmersion chamber 904.

In some embodiments, the fluid direction features direct flow from theimmersion chamber to other heat-generating components of the servercomputer that are not in the immersion chamber. In some embodiments, thefluid direction features direct flow toward another server computer. Forexample, the flow or overflow of liquid working fluid from an immersionchamber may flow into an immersion chamber of another server computer tocascade the liquid working fluid. The first server computer may bepositioned vertically above the second server computer to allow theliquid working fluid to flow from the immersion chamber of the firstserver computer to the immersion chamber of the second server computer.

In at least one embodiment, the server computers 1024-1, 1024-2, 1024-3may be oriented at an angle to gravity, as illustrated in FIG. 10 , suchas 5° or more relative to a vertical direction, to allow portion of theimmersion chamber 1004-1 of the first server computer 1024-1 to bepositioned above a portion of the immersion chamber 1004-2 of the secondserver computer 1024-2. In some embodiments, a first portion of theliquid working fluid 1008 that flows out of the immersion chamber 1004-1cascades into another immersion chamber 1004-2, 1004-3 and a secondportion of the liquid working fluid 1008 that flows out of the immersionchamber 1004-1 flows toward another heat-generating component 1042 ofthe server computer that is not in the immersion chamber to cool theheat-generating component 1042. In some embodiments, tilting thesubstrate and shell has the additional benefit of directing vaporbubbles away from the heat-generating components to reduce and/orprevent dryout.

FIG. 11 is a side schematic view of a server computer 1124 with aplurality of shells 1126-1, 1126-2, 1126-3 connected thereto. In someembodiments, the fluid direction features 1172-1, 1172-2 direct flow oroverflow from a first immersion chamber 1104-1 on a server computer to asecond immersion chamber 1104-2 on the same server computer. The firstimmersion chamber and second immersion chamber may be part of the sameshell connected to the substrate of the server computer. In otherexamples, the first immersion chamber is defined by a first shell andthe substrate of the server computer, and the second immersion chamberis defined by a second shell and the substrate of the server computer.

The fluid direction features of each chamber direct flow or overflowinto subsequent immersion chambers on the server computer. The immersionchambers may, therefore, slow the flow of the liquid working fluid inthe region adjacent the greatest heat-generating components on theserver computer while reducing the use of working fluid in locationswhere the additional cooling capacity is not needed.

INDUSTRIAL APPLICABILITY

The present disclosure relates generally to systems and methods forthermal management of electronic devices or other heat-generatingcomponents. Immersion chambers surround or partially surround theheat-generating components in a liquid working fluid, which conductsheat from the heat-generating components to cool the heat-generatingcomponents. As the working fluid absorbs heat from the heat-generatingcomponents, the temperature of the working fluid increases and theworking fluid may vaporize, introducing vapor into the liquid of theworking fluid. The vapor will rise due to buoyancy in the oppositedirection of gravity, rising out of the liquid working fluid andentering a headspace above the liquid working fluid.

An immersion cooling system according to the present disclosure includesan immersion chamber with a working fluid positioned therein. Theworking fluid transitions between a liquid phase and a vapor phase toremove heat from hot or heat-generating components in the chamber. Theliquid phase more efficiency receives heat from the components and, upontransition to the vapor phase, the working fluid can be cooled andcondensed to extract the heat from the working fluid before the workingfluid is returned to the liquid immersion bath at a lower temperature.

In some embodiments, the immersion bath of the liquid working fluid hasa plurality of heat-generating components positioned in the liquidworking fluid. The liquid working fluid surrounds the heat-generatingcomponents and other objects or parts attached to the heat-generatingcomponents. In some embodiments, the heat-generating components arepositioned in the liquid working fluid on one or more supports. In someexamples, the support is a motherboard of a computing device. Thesupport may support one or more heat-generating components in the liquidworking fluid and allow the working fluid to move around theheat-generating components. In some embodiments, the support isthermally conductive to conduct heat from the heat-generatingcomponents. The support(s) may increase the effective surface area fromwhich the working fluid may remove heat through convective cooling. Insome embodiments, one or more of the heat-generating components includesa heat sink or other device attached to the heat-generating component toconduct away thermal energy and effectively increase the surface area ofthe heat-generating component.

As described, conversion of the liquid working fluid to a vapor phaserequires the input of thermal energy to overcome the latent heat ofvaporization and may be an effective mechanism to increase the thermalcapacity of the working fluid and remove heat from the heat-generatingcomponents. Because the vapor rises in the liquid working fluid, thevapor phase of the working fluid accumulates in an upper vapor region ofthe chamber. Conventionally, a condenser cools part of the vapor of theworking fluid back into a liquid phase, removing thermal energy from thesystem and reintroducing the working fluid into the immersion bath ofthe liquid working fluid. The condenser radiates or otherwise dumps thethermal energy from the working fluid into the ambient environment orinto a conduit to carry the thermal energy away from the cooling system.Conventionally, the condenser is positioned in a headspace above theliquid immersion bath to condense the vapor working fluid down into theimmersion bath. This requires a large amount of volume and/or spaceabove the immersion bath at or near a lid of the immersion tank.

In some embodiments, the heat-generating components are positioned inthe liquid working fluid with at least a portion of the heat-generatingcomponents protruding from the liquid working fluid into the headspace.In some embodiments, the heat-generating components are completelysubmerged in the liquid working fluid. While submerging theheat-generating components may allow for efficiency thermal transfer tothe liquid working fluid, the portion of the heat-generating componentsthat protrudes into the headspace may allow for direct condensationand/or delivery of condensate on the heat-generating components.

In some embodiments, the liquid working fluid receives heat in a coolingvolume of working fluid immediately surrounding the heat-generatingcomponents. The cooling volume is the region of the working fluid(including both liquid and vapor phases) that is immediately surroundingthe heat-generating components and is responsible for the convectivecooling of the heat-generating components. In some embodiments, thecooling volume is the volume of working fluid within 5 millimeters (mm)of the heat-generating components.

The working fluid has a boiling temperature below a critical temperatureat which the heat-generating components experience thermal damage. Forexample, the heat-generating components may be computing components thatexperience damage above 100° Celsius (C). In some embodiments, theboiling temperature of the working fluid is less than a criticaltemperature of the heat-generating components. In some embodiments, theboiling temperature of the working fluid is less about 90° C. In someembodiments, the boiling temperature of the working fluid is less about80° C. In some embodiments, the boiling temperature of the working fluidis less about 70° C. In some embodiments, the boiling temperature of theworking fluid is less about 60° C. In some embodiments, the boilingtemperature of the working fluid is at least about 35° C. In someembodiments, the working fluid includes water. In some embodiments, theworking fluid includes glycol. In some embodiments, the working fluidincludes a combination of water and glycol. In some embodiments, theworking fluid is an aqueous solution. In some embodiments, the workingfluid is an electronic liquid, such as FC-72 available from 3M, orsimilar non-conductive fluids. In some embodiments, the heat-generatingcomponents, supports, or other elements of the immersion cooling systempositioned in the working fluid have nucleation sites on a surfacethereof that promote the nucleation of vapor bubbles of the workingfluid at or below the boiling temperature of the working fluid. Similarto a cold plate or cold surface in a conventional condenser, thedroplets are the subcooled surface that allow condensation upon thedroplets themselves.

Working fluid is recycled through the thermal management system, and, insome embodiments, the working fluid is a dielectric fluid or other fluidthat is expensive. A thermal management system that uses less workingfluid and/or uses the working fluid more efficiently allows for costsavings in the working fluid. In some embodiments, the working fluid isrelatively dense and containing large volumes of the working fluidrequires a strong container. Building and maintaining containers forlarge volumes and/or masses of working fluid can increase constructioncosts and container weight, which limits transport and maintenance ofthe containers.

In some embodiments according to the present disclosure, a shell isattached to a server computer or other electronic device to capture andpool the liquid working fluid adjacent to at least one heat-generatingcomponent of the server computer in an immersion chamber. In someembodiments, the shell is a stamped metal or polymer sheet. In someembodiments, the shell is an injection molded sheet. The shell may haveplanar or curved surfaces to define a portion of the immersion chamber.In some embodiments, the shell defines a portion of a rectangular prismor box-shaped immersion chamber around the heat-generating electroniccomponents. In some embodiments, at least a portion of the shell iscontoured to follow the shape of the heat-generating electroniccomponents.

In some embodiments, the shell contacts the server computer or asubstrate of the server computer along a bottom side and lateral wallsof the immersion chamber to collect the liquid working fluid. A top sideof the shell has an opening therein to the immersion chamber. The topside of the shell is the side, edge, or portion of the shell that isoriented upward relative to a direction of gravity such that vaporworking fluid bubbles rise through the immersion chamber toward the topside. In some embodiments, the opening in the top side allows the vaporworking fluid to exit the immersion chamber. In some embodiments, thetop side is a planar surface of the shell. In some embodiments, the topside follows a top edge of the shell.

The opening allows liquid working fluid to be introduced to theimmersion chamber and fill the immersion chamber with liquid workingfluid. In some embodiments, the incoming liquid working fluidcontinuously fills the immersion chamber to prevent a liquid level ofthe liquid working fluid from falling below the heat-generatingcomponents. In some embodiments, the incoming liquid working fluidcontinuously fills the immersion chamber to prevent a liquid level ofthe liquid working fluid from falling below the lowest part of theopening. For example, the incoming liquid working fluid may continuouslyfill the immersion chamber such that liquid working fluid spills out ofthe immersion chamber by overflowing the opening, leaking from a contactinterface, exiting through one or more apertures or perforations,through a drain, or combinations thereof.

In some embodiments, a portion of the liquid working fluid continuouslyoverflows from the opening as incoming liquid working fluid flows intothe immersion chamber through the opening. A flow rate of the incomingliquid working fluid is at least greater than vaporization rate of theliquid working fluid in the immersion bath. In other words, more liquidworking fluid mass is introduced into the immersion bath that is boiledby the heat-generating components, such that at least a portion of theliquid working fluid is displaced from the immersion bath by theincoming liquid working fluid.

In some embodiments, at least part of the liquid working fluid flows outof the immersion bath through one or more apertures, gaps, orperforations in the lateral walls and/or bottom side of the immersionchamber. For example, a contact interface between the shell and theserver computer may be not liquid tight, and allows at least a portionof the liquid working fluid in the immersion chamber to flow out of theimmersion chamber at the contact interface between the shell and thesubstrate of the server computer. In some embodiments, the shellincludes one or more perforations through the shell, itself, that allowsliquid working fluid to leak through perforations. In some embodiments,the shell includes a drain that may be selectively opened or closed toadjust the volume of liquid cooling fluid overflowing from the openingof the immersion chamber.

As described herein, the incoming working fluid may be colder than theliquid working fluid in the immersion chamber, and the colder incomingworking fluid may cool the heat-generating components more efficiently.Allowing at least a portion of the liquid working fluid to exit theimmersion chamber through gaps, perforations, or drains in the shell orimmersion chamber may allow greater mixing of the liquid working fluidin the immersion chamber, and, therefore, a lower average temperature ofthe liquid working fluid in the immersion chamber.

In some embodiments, a flow rate of the incoming liquid is greater thanvaporization rate of the liquid working fluid in the immersion bath anda flow rate of all liquid flow out of the immersion chamber other thanoverflow through the opening, such that the liquid level of theimmersion chamber remains above the heat-generating components and/or atthe lowest point of the opening.

The server computer may have a plurality of heat-generating electroniccomponents affixed to a substrate, such as a motherboard. Someelectronic components may consume more power and/or generate more heatthan other components. The greatest heat-generating components of theserver computer may be immersed in liquid working fluid, while lesserheat-generating components may be cooled through ambient gas cooling(e.g., a fan blowing on the lesser heat-generating components) orthrough overflow liquid working fluid flowing from the immersion chamberdefined by the shell.

The liquid working fluid introduced into the immersion chamber has atemperature less than the boiling temperature of the working fluid. Whena portion of the working fluid overflows from the immersion chamber, theoverflow liquid working fluid will still have an average temperaturebelow the boiling temperature. The overflow liquid working fluid maythen cool the lesser heat-generating components by absorbing heat fromthe lesser heat-generating components before boiling.

In some embodiments, the tank includes condensers positioned in thevapor space of the tank above a liquid collection area. At least aportion of the condenser may be positioned in the bottom half of thecollection tank. In some embodiments, all of the coils or cold plates ofthe condenser may be positioned in the bottom half of the collectiontank. In some embodiments, at least a portion of the condenser may bebelow the opening in the immersion chamber defined by the shell. In someembodiments, all of the coils or cold plates of the condenser may bebelow the opening in the immersion chamber defined by the shell.

Vapor working fluid condensed by the condensers falls to a collectionarea in the bottom of the collection tank. The collection area alsocollects the liquid working fluid that is displaced from the immersionchamber. The collected liquid working fluid may be returned to theimmersion chamber through a liquid return line. In some embodiments, theliquid working fluid may be further cooled while passing through theliquid return line before re-entering the immersion chamber.

By lowering the condensers in the collection tank, less headspace isrequired above the server computers, which reduces the size of thecollection tanks needed to house the components. For example, thecondensers can be move away from the lid, allowing the lid to be lighterand easier to remove to access the interior volume of the thermalmanagement system.

In some embodiments, lowering the condensers in the collection tankallows the condensers to more efficiently condense the vapor workingfluid. The vapor working fluid may be denser that non-condensable gases,such as nitrogen, that may enter the collection tank. Thenon-condensable gases can collect above the server computer(s) and theimmersion tank(s) while the vapor working fluid settles lower in thecollection tank. The condensers may be positioned in the area of thecollection tank with a higher concentration of the vapor working fluid.

The presence of non-condensable gases can adversely affect theperformance of the thermal management system, as the condensation of thevapor working fluid to a liquid working fluid lowers the pressure in thecollection tank, helping to draw the incoming liquid working fluid intothe collection tank. For example, the liquid working fluid may be over100 times denser (i.e., take up less than 1/100^(th) of the volume) thanvapor working fluid. In some embodiments, the non-condensable fluidsseparating into the headspace above the top of the immersion chambersand/or the server computers can allow the non-condensable gases to bevented, pumped, or otherwise purged from the collection tank moreefficiently.

In some embodiments, removing at least a portion of the server computersor other electronic devices from the immersion bath or collection bathcan maintain a cleaner, and, therefore, more efficient, working fluid.For example, the elastomers found in electronic connectors, wires,cables, or other components can leach into the liquid working fluid morereadily than into the vapor working fluid. The leached elastomers canadversely affect the thermal absorption efficiency of the working fluid,adversely affect the viscosity of the working fluid, adversely affectthe boiling temperature of the working fluid, or cause the working fluidto leave a deposit on the heat-generating components, which canadversely affect the thermal transfer (e.g., cooling) from theheat-generating components.

In some embodiments, data connectivity may be improved by positioningthe connectors of the server computer in a gaseous environment relativeto a liquid environment. For example, optical connections, such as fiberoptics, may perform better and/or more predictably in a gaseousenvironment relative to a liquid environment due to differences in theindex of refraction between the optical fibers and the liquidenvironment.

In a conventional immersion tank, the liquid pressure increases as depthof the immersion bath increases. In conventional tanks and fluids, adepth of 1 meter results in a 2.3 pounds per square inch (PSI) increase.The increased pressure results in an increase in the boiling point forthe working fluid and a resulting temperature increase of the componentsadjacent the working fluid at the bottom of the immersion bath. Whenseparate immersion chambers are placed around heat-generatingcomponents, and/or the boards are oriented horizontally, the columnarpressure of the fluid around the component is reduced and produces loweroperating temperatures for the component. In at least one example, aworking fluid exhibits a 4° C. decrease in temperature relative to acomponent at a depth of 1 meter in a conventional immersion tank.

The incoming liquid working fluid is delivered by, in some embodiments,a manifold that directs the incoming liquid working fluid into theimmersion chamber. In some embodiments, the incoming liquid workingfluid is introduced through the opening in the top surface of theimmersion chamber. In some embodiments, the incoming liquid workingfluid is introduced through a port in shell, such as in the lateral wallof the immersion chamber. The incoming liquid working fluid may displacethe liquid working fluid in the immersion chamber, at least partially,out the opening in the top.

The manifold may provide incoming liquid working fluid to each of theshells and immersion chambers, individually. The individual immersionchamber for each server computer is a more efficient allocation ofworking fluid while also providing modularity in the thermal managementsystem for maintenance and repairs.

In some embodiments, the manifold can provide a plurality of streams ofincoming liquid working fluid that are directed at the immersion chamberto fill the immersion chamber. The plurality of streams may allow foradditional cooling on other lesser heat-generating components. Theplurality of streams may provide greater turbulence and mixing of theincoming liquid working fluid with the liquid working fluid in theimmersion chamber to limit and/or prevent temperature gradients in theimmersion chamber.

In some embodiments, the condenser includes a plurality of cooling pipesor cooling rods. The condenser most efficiently cools and condensesvapor immediately adjacent to a surface of the pipes or rods. In someembodiments, deflectors are positioned below at least one of the pipesor rods to catch condensate. The deflector limits and/or prevents thecondensate from falling onto the pipe or rod below, which would coat,and adversely affect the condensation efficiency of, the subsequent pipeor rod.

In some embodiments, at least a portion of the heat-generatingcomponents in the immersion cooling system protrude above the immersionbath of liquid working fluid. Cooling of the heat-generating componentsmay be assisted by the spraying of liquid working fluid toward and/orabove the heat-generating components. In some embodiments, a fluidconduit carries liquid working fluid from the collection bath or otherreservoir of liquid working fluid to at least one nozzle, such as on themanifold described herein. The liquid working fluid is ejected from thenozzle(s) in droplets toward an immersion chamber and/or othercomponents of the server computers.

The nozzles may be configured and/or sized to produce droplets of adesired diameter. The nozzles may be adjustable to vary the size of thedroplets depending upon desired flowrate through the nozzles and thedesired droplet size. In some embodiments, the nozzles create aplurality of droplets with an average droplet diameter of less than 1millimeter. In some embodiments, the nozzles create a plurality ofdroplets with an average droplet diameter of less than 0.5 millimeters.In some embodiments, the nozzles create a plurality of droplets with anaverage droplet diameter of less than 0.25 millimeters. In someembodiments, the nozzles create a plurality of droplets with an averagedroplet diameter of less than 0.1 millimeters. In some embodiments, thenozzles sprays the subcooled working fluid onto another component, suchas a fan, which further disrupts the surface tension and creates thedroplets and/or more droplets to introduce the liquid working fluid tothe server computers.

To further improve efficiency of working fluid allocation, in someembodiments, the shell is complementarily shaped to a topography of atleast one heat-generating component. For example, the heat-generatingcomponents may protrude from the substrate by different degrees, such asa memory module protruding farther than a processor. In someembodiments, the shell is complementarily shaped to the heat-generatingcomponents to maintain a substantially constant distance from theheat-generating components and, therefore, a substantially constantamount of liquid working fluid around the heat-generating components. Insome embodiments, the shell includes a vapor direction feature on aninner surface thereof to collect and direct the vapor bubbles around orthrough the heat-generating components to reduce dryout as the vaporbubbles rise through the immersion chamber.

The shell may be supported against or adjacent to the server computerand/or substrate by a frame. In some embodiments, the frame is a chassisof the server computer. In some embodiments, the frame is supported byor supports the chassis of the server. In some embodiments, the framedefines at least part of the immersion chamber, such as a lateral wallof the immersion chamber.

Collecting liquid working fluid adjacent to each server computer in arack or collection tank simplifies maintenance and/or modifications tothe server array. In a conventional immersion cooling system, the entireimmersion tank may be drained to access a component. In a conventionalimmersion cooling system, removing one server computer or othercomponent removes volume from the immersion tank, lower the liquid levelof the immersion bath, which may expose other components to a reductionin cooling capacity. A thermal management system according to thepresent disclosure allows each server computer to have discreteimmersion chambers for each server computer, allowing the cooling ofeach server computer to be independent of the presence or removal ofother components or computers.

A reduction in liquid working fluid mass, and liquid working fluid levelin the collection tank, reduces the hydrostatic pressure against thewalls of the immersion chamber. For example, replacing the liquidworking fluid in the tank with vapor working fluid may reduce thepressure on the collection tank by over 100 times, allowing for lighter,smaller, and cheaper tanks to be used. In some embodiments, the workingfluid is 1.8 times to 2.0 times denser than water. Less working fluidmass means less hydrostatic pressure and less likelihood of leaks orother failures of the collection tank.

In some embodiments, the condenser is positioned on a bottom or a sideof the collection tank. Because the liquid level of the collection areais lower than the server computers and the immersion chambers, theserver computers can be accessed and/or removed from the collection tankthrough a top of the collection tank without moving or turning off thecondenser. In some embodiments, the liquid working fluid can continuecycling through the liquid return line and through the manifold evenwhile one or more server computer and shell assemblies is removed orreplaced, reducing downtime and preventing the need for virtual machinemigration.

While vertical access to the server computer and/or thermal managementsystem is possible from the top with some embodiments of the presentdisclosure, some embodiments of collection tanks allow access to thecollection tank, server computers, connectors, other components, orcombinations thereof through a front or side surface of the collectiontank. For example, one or more movable or removable access panels in aside wall of the collection tank may have a bottom edge that is higherthat a liquid level of the collection bath at the bottom of thecollection tank. In some embodiments, the bottom edge of the accesspanel may be higher than the liquid level to retain the relatively densevapor working fluid in the collection tank.

Various embodiments and arrangements of components may be used toperform thermal management using a continuous flooding of liquid workingfluid. In some embodiments, a method of thermal management according tothe present disclosure includes introducing a first amount of liquidworking fluid to a liquid immersion bath in contact with aheat-generating component and boiling at least a vaporized portion ofthe liquid working fluid with the heat-generating component. The liquidworking fluid absorbs heat from the heat-generating components andincreases in temperature until reaching the boiling temperature. Theliquid working fluid absorbs heat to exceed the latent heat needed totransition states to a gas.

While a vaporized portion of the working fluid transitions to a vaporand rises out of the liquid immersion bath from around theheat-generating components, another portion of the liquid working fluidin the immersion bath is removed from the immersion bath. In someembodiments, the method includes removing from the liquid immersion batha second amount of liquid working fluid less than the first amount thatis introduced into the liquid immersion bath. By removing the secondamount of liquid working fluid from the immersion bath while introducingthe first amount, the immersion bath cycles liquid working fluid. Insome embodiments, the incoming liquid working fluid is colder than theoutgoing liquid working fluid, lowering the temperature of the immersionbath.

In some embodiments, the mass of the first amount of liquid workingfluid is equal to the mass of the vaporized portion and the secondamount of liquid working fluid. In some embodiments, the second amountis removed from the liquid immersion bath by at least one of overflowfrom an opening at the top of the immersion chamber, flow out of one ormore contact interfaces between a shell and the computing device, flowout of one or more apertures or perforations in the shell or computingdevice, or through a drain that selectively opened or adjusted tocontrol flow therethrough.

The method may further include directing the second amount of the liquidworking fluid toward or onto other heat-generating components. In someembodiments, a shell and/or computing device that define an immersionchamber includes fluid direction features to control the flow oroverflow of the liquid working fluid upon exiting the immersion chamber.

While embodiments of vertically oriented server computers and shellshave been describe herein, in some embodiments, the substrate of theserver computer and/or the shell are oriented substantiallyhorizontally. For example, the horizontal shell may have a top surfacewith an opening that is larger in area that a vertically oriented shelland server computer. The horizontal server computer and heat-generatingcomponent, in combination with a larger opening, allows the vapor toexit the immersion chamber more efficiently. The horizontal servercomputer and heat-generating component, in combination with a largeropening, may reduce dryout and increase cooling efficiency.

In some embodiments, the shell includes at least one fluid directionfeature, such as a channel, groove, notch, opening, fin, wall, slot,tunnel, or other structure integrated into or located on a surface ofthe shell. The fluid direction feature influences the direction of theliquid working fluid as the liquid working fluid exits the immersionchamber. In some embodiments, a surface of the server computer and/orsubstrate of the server computer includes at least one fluid directionfeature to further direct the liquid working fluid toward aheat-generating component located outside of the immersion chamber.

In some embodiments, the fluid direction features direct flow from theimmersion chamber to other heat-generating components of the servercomputer that are not in the immersion chamber. In some embodiments, thefluid direction features direct flow toward another server computer. Forexample, the flow or overflow of liquid working fluid from an immersionchamber may flow into an immersion chamber of another server computer tocascade the liquid working fluid. The first server computer may bepositioned vertically above the second server computer to allow theliquid working fluid to flow from the immersion chamber of the firstserver computer to the immersion chamber of the second server computer.

In at least one embodiment, the server computers may be oriented at anangle to gravity, such as 5° or more relative to a vertical direction,to allow portion of the immersion chamber of the first server computerto be positioned above a portion of the immersion chamber of the secondserver computer. In some embodiments, a first portion of the liquidworking fluid that flows out of the immersion chamber cascades intoanother immersion chamber and a second portion of the liquid workingfluid that flows out of the immersion chamber flows toward anotherheat-generating component of the server computer that is not in theimmersion chamber to cool the heat-generating component.

In some embodiments, the fluid direction features direct flow oroverflow from a first immersion chamber on a server computer to a secondimmersion chamber on the same server computer. The first immersionchamber and second immersion chamber may be part of the same shellconnected to the substrate of the server computer. In other examples,the first immersion chamber is defined by a first shell and thesubstrate of the server computer, and the second immersion chamber isdefined by a second shell and the substrate of the server computer.

The fluid direction features of each chamber direct flow or overflowinto subsequent immersion chambers on the server computer. The immersionchambers may, therefore, slow the flow of the liquid working fluid inthe region adjacent the greatest heat-generating components on theserver computer while reducing the use of working fluid in locationswhere the additional cooling capacity is not needed.

The present disclosure relates to systems and methods for coolingheat-generating components of a computer or computing device accordingto at least the examples provided in the sections below:

[A1] In some embodiments, a thermal management system includes a servercomputer and a shell defining an immersion chamber. The shell contactsthe server computer along a bottom side and lateral walls of thechamber, and the immersion chamber has an opening on a top side. Theshell is connected to the server computer and a portion of the servercomputer defines at least a portion of the immersion chamber.

[A2] In some embodiments, the server computer of [A1] includes asubstrate, and the shell is connected to the substrate.

[A3] In some embodiments, the top side of [A1] or [A2] is parallel tothe substrate.

[A4] In some embodiments, the server computer of any of [A1] through[A3] includes a heat-generating component, and the opening of the topside of the immersion chamber is vertically above the heat-generatingcomponent.

[A5] In some embodiments, a thermal management system of any of [A1]through [A4] includes a working fluid positioned in the immersionchamber. The working fluid fills the immersion chamber to the opening.

[A6] In some embodiments, the server computer of any of [A1] through[A5] includes a first heat-generating component and a secondheat-generating component, and the first heat-generating component is inthe immersion chamber and the second heat-generating component isoutside of the immersion chamber.

[A7] In some embodiments, the server computer of any of [A1] through[A6] includes a heat-generating component and at least a portion of theshell is complementarily shaped to a topography of the heat-generatingcomponent.

[A8] In some embodiments, the shell of any of [A1] through [A7] has atleast one fluid direction feature on an outer surface thereof.

[B1] In some embodiments, an immersion cooling system includes acollection tank with a collection area, a substrate having at least oneheat-generating electronic component thereon, and a shell defining animmersion chamber. The shell contacts the server computer along a bottomside and lateral walls of the chamber, and the immersion chamber has anopening on a top side. The shell is connected to the server computer anda portion of the server computer defines at least a portion of theimmersion chamber. The substrate and heat-generating componentpositioned in the collection tank and above the collection area.

[B2] In some embodiments, the immersion cooling system of [B1] includesa condenser positioned in the collection tank below the opening of theimmersion chamber.

[B3] In some embodiments, the immersion cooling system of [B1] includesa condenser positioned in a bottom half of the collection tank.

[B4] In some embodiments, the immersion cooling system of any of [B1]through [B3] includes a manifold configured to receive liquid workingfluid from the collection area and direct the liquid working fluid tothe immersion chamber.

[B5] In some embodiments, the shell of [B4] is configured to connect tothe manifold to receive the liquid working fluid.

[B6] In some embodiments, the manifold of [B4] is configured to directthe liquid working fluid into the opening of the immersion chamber.

[B7] In some embodiments, the immersion cooling system of any of [B1]through [B6] includes a non-condensable gas vent in the collection tank.

[B8] In some embodiments, a height of a headspace of the immersioncooling system of any of [B1] through [B7] is less than a width of thecollection tank.

[C1] In some embodiments, a method of thermal management of electroniccomponents includes introducing a first amount of liquid working fluidto a liquid immersion bath in contact with a heat-generating componentof a computing device, boiling at least a vaporized portion of theliquid working fluid with the heat-generating component, and removing asecond amount of liquid working fluid less than the first amount.

[C2] In some embodiments, at least part of the second amount of liquidworking fluid of [C1] leaks out of the liquid immersion bath between ashell and a substrate.

[C3] In some embodiments, at least part of the second amount of liquidworking fluid of [C1] or [C2] overflows from a top side of the shell.

[C4] In some embodiments, the method of any of [C1] through [C3]includes condensing the vaporized portion with a condenser below theliquid immersion bath.

The articles “a,” “an,” and “the” are intended to mean that there areone or more of the elements in the preceding descriptions. The terms“comprising,” “including,” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements. Additionally, it should be understood that references to “oneembodiment” or “an embodiment” of the present disclosure are notintended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features. For example, anyelement described in relation to an embodiment herein may be combinablewith any element of any other embodiment described herein. Numbers,percentages, ratios, or other values stated herein are intended toinclude that value, and also other values that are “about” or“approximately” the stated value, as would be appreciated by one ofordinary skill in the art encompassed by embodiments of the presentdisclosure. A stated value should therefore be interpreted broadlyenough to encompass values that are at least close enough to the statedvalue to perform a desired function or achieve a desired result. Thestated values include at least the variation to be expected in asuitable manufacturing or production process, and may include valuesthat are within 5%, within 1%, within 0.1%, or within 0.01% of a statedvalue.

A person having ordinary skill in the art should realize in view of thepresent disclosure that equivalent constructions do not depart from thespirit and scope of the present disclosure, and that various changes,substitutions, and alterations may be made to embodiments disclosedherein without departing from the spirit and scope of the presentdisclosure. Equivalent constructions, including functional“means-plus-function” clauses are intended to cover the structuresdescribed herein as performing the recited function, including bothstructural equivalents that operate in the same manner, and equivalentstructures that provide the same function. It is the express intentionof the applicant not to invoke means-plus-function or other functionalclaiming for any claim except for those in which the words ‘means for’appear together with an associated function. Each addition, deletion,and modification to the embodiments that falls within the meaning andscope of the claims is to be embraced by the claims.

It should be understood that any directions or reference frames in thepreceding description are merely relative directions or movements. Forexample, any references to “front” and “back” or “top” and “bottom” or“left” and “right” are merely descriptive of the relative position ormovement of the related elements.

The present disclosure may be embodied in other specific forms withoutdeparting from its spirit or characteristics. The described embodimentsare to be considered as illustrative and not restrictive. The scope ofthe disclosure is, therefore, indicated by the appended claims ratherthan by the foregoing description. Changes that come within the meaningand range of equivalency of the claims are to be embraced within theirscope.

What is claimed is:
 1. A thermal management system comprising: a servercomputer; and a shell defining an immersion chamber, wherein the shellcontacts the server computer along a bottom side and lateral walls ofthe chamber, and the immersion chamber has an opening on a top side, andwherein a portion of the server computer defines at least a portion ofthe immersion chamber.
 2. The thermal management system of claim 1,wherein the server computer includes a substrate, and the shell isconnected to the substrate.
 3. The thermal management system of claim 2,wherein the top side is parallel to the substrate.
 4. The thermalmanagement system of claim 1, wherein the server computer includes aheat-generating component, and the opening of the top side of theimmersion chamber is vertically above the heat-generating component. 5.The thermal management system of claim 1, further comprising a workingfluid positioned in the immersion chamber and filling the immersionchamber to the opening.
 6. The thermal management system of claim 1,wherein the server computer includes a first heat-generating componentand a second heat-generating component, and the first heat-generatingcomponent is in the immersion chamber and the second heat-generatingcomponent is outside of the immersion chamber.
 7. The thermal managementsystem of claim 1, wherein the server computer includes aheat-generating component and at least a portion of the shell iscomplementarily shaped to a topography of the heat-generating component.8. The thermal management system of claim 1, wherein the shell has atleast one fluid direction feature on an outer surface thereof.
 9. Animmersion cooling system comprising: a collection tank with a collectionarea; a substrate having at least one heat-generating electroniccomponent thereon, the substrate and heat-generating componentpositioned in the collection tank and above the collection area; a shelldefining an immersion chamber, wherein the shell contacts the servercomputer along a bottom side and lateral walls of the chamber, and theimmersion chamber has an opening on a top side, and wherein a portion ofthe server computer defines at least a portion of the immersion chamber,10. The immersion cooling system of claim 9, further comprising acondenser positioned in the collection tank below the opening of theimmersion chamber.
 11. The immersion cooling system of claim 9, furthercomprising a condenser positioned in a bottom half of the collectiontank.
 12. The immersion cooling system of claim 9, further comprising amanifold configured to receive liquid working fluid from the collectionarea and direct the liquid working fluid to the immersion chamber. 13.The immersion cooling system of claim 12, wherein the shell isconfigured to connect to the manifold to receive the liquid workingfluid.
 14. The immersion cooling system of claim 12, wherein themanifold is configured to direct the liquid working fluid into theopening of the immersion chamber.
 15. The immersion cooling system ofclaim 9, further comprising a non-condensable gas vent in the collectiontank.
 16. The immersion cooling system of claim 9, wherein a headspaceabove the heat-generating component is less than a width of thecollection tank.
 17. A method of thermal management comprising:introducing a first amount of liquid working fluid to a liquid immersionbath in contact with a heat-generating component of a computing device;boiling at least a vaporized portion of the liquid working fluid withthe heat-generating component; and removing a second amount of liquidworking fluid less than the first amount.
 18. The method of claim 15,wherein at least part of the second amount leaks out between a shell anda substrate.
 19. The method of claim 15, wherein at least part of thesecond amount overflows from a top side of a shell.
 20. The method ofclaim 15, further comprising condensing the vaporized portion with acondenser below the liquid immersion bath.